基于响应矩阵的RFQ新调谐算法的验证与实现

Verification and realization of a novel tuning algorithm for RFQs based on response matrix

射频四极场加速器(Radio Frequency Quadrupole,RFQ)广泛应用于质子加速器装置中,高频率、紧凑型RFQ的发展可以推动质子加速器装置的小型化,同时也面临调谐困难的问题。紧凑型RFQ的性能对腔体尺寸的敏感度高,基于理论物理特性的传统调谐算法难以取得良好效果,而基于腔体实际物理特性的调谐算法则可以解决紧凑型RFQ的调谐难点。本文提出了一种基于响应矩阵和最小二乘法的调谐算法,该算法可以限定求解的范围,避免计算结果超出调谐器可调谐范围的问题;为二极场分量赋予权重,可以高效地降低二极场误差,解决二极场分量难以调谐的问题。根据新的调谐算法分别在模拟环境下的RFQ样机上完成了调谐实验,在搭建的测量平台获得的结果显示:初始状态下二、四极场误差分别为24.09%和1.57%,经过5次调谐后两者误差分别降为2.33%和1.39%,验证了调谐算法的有效性。该调谐算法具有普适性,也可以用于其他频率的RFQ,将来还可以促进质子加速器装置的小型化,推动医用质子装置的普及。

[Background]Radio Frequency Quadrupoles(RFQs)are applied widely in proton accelerator facilities.The development of the high-frequency RFQs enables the construction of compact proton accelerator facilities,but faces with more tuning difficulties.The traditional tuning methods based on the theoretical characteristics of the RFQ cannot achieve good results with compact proton accelerators.The tuning method based on the response matrix and SVD method meets the problem of the solution being out of the range that tuners can reach.[Purpose]This study aims to purpose a novel tuning method for efficient reduction of dipole components by a transform of the tuning method,so as to tune the compact RFQs better and limit the range of the solution.[Methods]Firstly,a tuning method based on the response matrix and the least squares method was designed and implemented.The solution was limited,and a different weight was assigned to the dipole components for diminution during the tuning progress.Then,the tuning method was experimentally tested in the simulation environment on the aluminum RFQ prototype for verification.Both tuning with single tuner and multiple tuners were tested in simulation.[Results]Verification results show that high precision is achieved and the solution is within the expected range even without limitation.Experimental results of verification on the aluminum RFQ prototype show that the quadrupole and dipole component errors are 1.57%and 24.09%,respectively,in the initial state,but reduce to 1.39%and 2.33%,respectively,after five rounds of tuning.[Conclusions]The novel tuning method based on response matrix is verified by this study for its validity of limiting the range of the solution and reducing the dipole components efficiently,hence can be applied to RFQs operating at other frequencies as well.It can contribute to the development of compact proton accelerators and promote medical proton facilities in the future.